That's easy: either a crack, or a pop, depending on a handful of factors; you'll hear the difference when you encounter it. Language isn't flawed as much as it is incomplete. There are words missing for things perfectly commonplace not because there can't be any (because language is somehow flawed and incapable of transmitting those) but because there's little use to them. Here's a good example: what do you call the two lines on your face that come down from your nose to the extremes of your lips? It's not that there can't be a word - those lines happened to be meaningless to us, useless in daily life that we didn't bother to name them; when we have to, we call them long-hand "you know, those two lines that come down from nose to lips - yeah, those ones". Apparently, thinking of a name is more difficult or resource-inefficient in this situation. It's a fascinating condition that we've invented."Whats the sound of hand clapping?"